Technology and function with pellet heat!

Pellet burner

You can describe today's technology of pellet burners as devided into different categories. These three can be devided into three phases, such as under fed, horizontal fed and vertical fed. A under fed burner often has rotary vane feeders (with a small internal storage) and built-in dosage auger inside the burner unit, this also goes for the horizontal dosaged burner while the vertical solution on the burner has a fall shaft and the fuel is dosed directly by an external auger.
Under fed function
Horizontal fed function
Over fed function
Under fed technology
As shown on the picture to the right, the BioLine20 burner from EcoTec is a typical example of under fed burners. The burner calls for fuel from an external auger that drops down the fuel to the lock on the burner. The lock wheel and its valves then dose the pellets further down to the internal feed auger. Here the fuel is fed via the internal auger with even feeding intervals and puched up into the burner cup and combusted. At regular cleaning of heating surfaces, the burner cup should also be cleaned from ash residues from the combustion. The burner ignites the fuel automatically via a hot-air heater. This construction of burner requires space above the burner cup so that the flame does not reach the celing in the hearth.
Horizontal fed technology
PellEco 2000 is a typical horizontal fed burner. The burner has an internal storage dosed by an external auger. In the bottom of the internal storage a rotary vane feeder handles the dosage to the internal auger via a fall shaft. The fuel is being fed forward to the burner cup. This burner does not have electrical ignition but is lid with fire-lighting fluid and then burns with a so called maintencance fire. This construction of burner requires space above the burner cup, so that the flame does not reach the celing in the hearth. There are flame pointers so that the flame can be directed forward if needed. The burner has been tested with bark pellets and handles that well, since it more or less works as a stoker fed burner. This opens up new ways for a broader fuel option.
Over fed technology
As an example we find, to the right, the PX21 burner from Ariterm that function wise is a over fed pellet burner. The dosage is made via an external auger and therefore the burner, other than that, does not have any other movable details than the fan. When the boiler calls for heat via the own temperature giver of the burner, the burner is first being dosed with a so called start up dose. After that the fuel is ignited by a hot-air heater, in co-operation with the fan. During the heating phase the burner is dosed with a smaller amount of fuel that then changes to full operation. When the temperature of the boiler has been reached, the fuel feeding is disconnected and only the fan runs for a couple of minutes so that the fuel is fully combusted and the greater part of the ash is blown out in the hearth. The burner operates with start and stop and does not have a maintenance fire, but can be compared with the operation of an oil burner. The burner requires cleaning once a week to be cleaned from ash residues in the burner pipe.
1.Fall pipe
2.Hearth pipe
3.Terminals
4.Electronical steering
5.Combustion air fan
6.Hot-air ignition
Fuel dosage
Burner constructions that have an internal storage are not so sensitive and dependent on an even dosage of the fuel from the external auger to the burner, therefore this one requires less maintenance and can be fired longer periods. The fuel is being fed to the internal storage and by cell feeding and fall shaft the burner is then being dosed with an internal auger that gives a more exact dosage to achieve an even combustion. Burners with over fall shaft being dosed with the external auger are more depending on a more frequent cleaning of week storage and the external auger pipe approx. one to two times per year, to reach an even dasage. Please note that cleaning of storage and feeding augers should be made continuously and frequently regardless function of dosage to keep a problem free heating system. All bulk storages should be cleaned before every filling, to remove chip residues that could cause arching problems and wear of the augers.
Ignition function
If looking at the ignition function of the burners, it varies depending on what technology the burners operates with. The ignition of the burners, on most products, takes place with the help of a so called ignition element that could compared to a tubular element with a encapsulated resistance wire that is being heated up during a few minutes, and with the help of the fan that puches out hot air towards the fuel that is then being ignited. The life cykle on these products varies between 1,5 year up to 5 years depending on the rand. Some burner brands you have to ignite manually with a drop of fire-lighting fluid that then holds the flame alive by so called maintenance fire where the control system of the burner with even intervals goes in and feed pellets and adds oxygen with the fan. Though, you should be observant to that maintenance fire is not recommended when fireing against an accumulator tank, and this can cause unnecessary amount of soot during the Summer, when the draft condidtions often get worse at warmer outdoor temperatures, then a burner with automatic ignition is an advantage. The advantage with maintenance fire is that when using a lot of hot service water, this function gives a faster effect and keeps the temperature of the boiler more constant and balanced. Since burners with ignition element have a time before the the pellets have been ignited, and therefore cause the temperature of the boiler to sink to a lower level before it stabilizes.
Ash handling
Also the ash handling varies a lot between the different burner brands. As an example, BioNordic's B16GL has solved the problem with compressed air. Here there are two nozzles on the bottom of the fuel cup that go in and blow the burner clean before start-up. These nozzles are shaped so that they cut off slag residues and ash like air-knifes. The burner then also becomes less sensitive to bark pellets and peat pellets, that give a substancially larger amount of ash. Ulma AB has chosen stick sweeping on thier burner ULMA 2000, where you can easilly, when needed, turn a wheel to the left and bring the scraper back, turn it down again and push the scraper forward and clean the burner pipe from ash. This scraper also acts pellet brake so that the pellets stay in the combustion pipe.
Pellet stoves
The pellet stove is built to be a primary heat source i.e. be responsable for the main part of the heat demand of a house. It works fully automatic with a room thermostat and in best cases only needs to be filled one to two times per week, depending on model and heat demand. The stoves spread heat via fan system or water jacketed models that are connected to existing radiator system.
It is relatively easy to install since it can be instaled to simple gas flues and at the same time it is a simple construction that does not require any bearing foundations. Security against back fire goes for the three of each other independent systems for the security required by the the P-marking.
It can easilly replace at least 70- 80 % of the electric heating demand in a normal sized house and operates best when at the lowest outdoor temperature. It is at the same time a nice furniture that spreads wellbeing and good comfort.
A pellet stove needs 50- 60 watt electricity (like a light-bulb) to work. With a simple convertor from 12V to 230V a pellet stove could work problem free for several days on an ordinary car battery. A welcome security for house-owners at power cuts.

Example of the function of a pellet stove
The pellet stoves can in most cases be delivered with different design to fit your home environment. The stoves are faced with everything from marble, colored sheet and soapstone etc. The stove can as a suggestion, be placed centrally in the house. Then the heat going up easilly spread further to the other rooms in the house. If you keep the doors open the temperature normally does not differ more than two degrees between the rooms. It works best in a house with open planning. This mostly applies to stoves that spread heat via fan systems.
Pellet boilers
Integrated pellet boilers operate with a high efficiency. Burner and boiler are put together to one unit. The pellet boiler is like a traditional boiler where you have built in a pellet burner inside the actual boiler. This is normally the best technology since the parts already from the beginning are adjusted to each other. Since a pellet boiler is specifically adjusted to the fuel you normally reach a better performance than when you put a burner in an existing boiler that is a couple of years old. As an example, below we can see the function of the integrated pellet boiler Bionet

Example of one of Ariterm's pellet systems
- complete from storage to boiler/burner.

Inside Ariterm's Bionet a compact pellet boiler has been combined with a BeQuem pellet burner to a reliable and efficient unit. Comfort, environmental preformance and efficiency are to the highest degree imaginable to meet the requirements of user-friendly and efficient pellet combustion.

The Bionet has a standing convection system that decreases the coating which makes the boiler able to keep a high efficiency between the service internvals. The service requirement depends on the pellet quilty and selected effect (fuel consumption) and veries between the sesons. It is the same when it comes to the maintenance requirement of the burner. The 20 litre ash box is of good size and is easy to pull out and empty.

Adjust automatics
It for pellet combustion, especially developed, automatics makes it possible to adjust the effect in up to 3 steps. In the display of the automatics, you can get informaiton about operating status such as boiler temperature, flue-gas temperature, pellet consumption, pellet storage, alarm function etc.
Many-sided additional heat
Bionet can with advantage be adjusted to an existing waterborned heating system. Bionet is a easily handled, handy and economic choice in combination with a modern oil boiler, wood boiler, heat pump or sun energy system. The effect of 12 kW is enough for most house systems. For hot service water, the Bionet is connected to a separate water heater. The compact format of the Bionet make an installation possible even in narrow spaces.